Influence of diffraction on hard-aperture Kerr-lens mode locking

It is demonstrated that with rigorous inclusion of diffraction on an intracavity hard aperture the values of the nonlinear differential loss coefficient Gamma (which characterizes the efficiency of Kerr-lens mode locking) are several times higher than in the commonly used simplified approach in which diffraction effects are neglected. Diffraction changes modal properties and causes a faster decrease of mode losses with increasing power than predicted by the traditional approach. With this correction, the discrepancy between the Kerr-lens mode-locking theory and the theoretical estimates of the self-starting condition is substantially decreased.